I was on the ground. At 280 feet. I live on the approach for 28L/R for planes coming from the Pacific and sometimes the Pacific NW. Four engine plane directly overhead. Noticed a stream of liquid coming out the bottom, quickly dissipating. During the 90 seconds or so I watched, the liquid always dissipated within two plane lengths. Immediately checked flightradar24 to see what plane it was to try to determine what might be going on.

Initially I thought it might have been fuel dump for an emergency landing, but upon determining the flight was likely NRT->SFO (and not something that had just taken off) thought unlikely the plane would be overweight. Further, I believe dump is from the wings, not the tail.